The first thing I would do is to try if Internet Explorer or Chrome work correctly on that HP with amazon.com. If they do, the problem is gone.
An alternative might be to reset Firefox to defaults and try again. https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings tells how.
Whenever I go on my Amazon site and browse, I eventually get a white screen with my cursor showing an hourglass. My only option is to close the window. When I reopen Firefox 44, I get a dialog box asking if I want to de-bug the script, continue, or stop the script. I stop the script and I'm allowed to continue for a few seconds and then it happens again.
I have two laptops in the same room running off of the same wifi. One is an Asus with Windows 8.1 and the other is an HP with Windows 7. The problem only occurs on the HP with Windows 7. It's keeping me from doing business with Amazon on that laptop. How can I get rid of this problem?